Determatan sulfate molecules exist in three molecular helical conformations with screw symmetries 21, 85, 32. We would like to determine the details of these structures and the way in which the polyanions are packed in their respective crystal structures. Although all these forms have been obtained with nominally sodium salts, we now know from our work with hyaluronate and chondroitin sulfate that the kind of cations present can have dramatic effects on the molecular conformations of glycosaminoglycans. By examining pure Na ion and Ca 2 ion salts, we hope to determine whether this is the case also for dermatan sulfate. If appropriate, we will attempt to find the cation positions in the crystal structures to rationalize their effects as we have done for other mucopolysaccharides. We hope also to complete the molecular and crystal structure determinations of several Klebsiella polysaccharides (serotypes K5, K8, K38) for which we have X-ray diffraction patterns of oriented and polycrystalline specimens.